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MG MGA - Master Cylinder Rebuild - pistons stuck?

I rebuilt my master cylinder tonight. The sleeves were redone once before, I guess, as they are in bronze. A light honing, new seals from Moss, and everything was back together. However, when I pushed the pistons in using the rods, they didn't return. Is this normal? They seem tight to me. BTW, I assembled with silicone brake fluid for lubrication ... not dry.
Rich

Search the archives, a common problem. The seals are the wrong size for the bores.
dominic clancy

Your M/C was rebuilt by White Post Restorations. The pistons are std size. Some M/C's use a slightly larger piston/seal combination as in my current M/C. If I were to do mine again, I would not have gone with the oversized M/C.

I have had a problem with bad parts from the "usual suppliers" as to the suitability of their seal kits.

Not to start a flame war, it is reported (meaning that I have no personal knowledge) that the silicone fluid does not have the lubricity of the traditional Castrol LMA or other DOT 3 and DOT 4 fluids.

Chuck
Chuck Schaefer

The new seal kit from Moss was the guilty party. All of the new pieces were identically sized to the old ones, with the exception of the rubber piece that fits around the piston.

This piece had the identical inner diameter, but the outer diameter was 1/16" larger. The old seal (in very good shape) produced a tight fit into the cylinder. The new seal produced an extra tight fit into the cylinder. The old one worked, the new one locked the pistons in place. So I used the old seals and the M/C works great now!

Doesn't Moss know about this problem? Or do they really think that their seals are a perfect reproduction?

R Stokes

I actually had that problem with a different supplier. I found that the Moss seals were ok. I don't think it's a problem related to a specific retailer, but rather problems with their suppliers concerning quality control.
Mark

Rich,
If you find a problem and tell them, then they will know about the problem. If you don't, then you have to assume that nobody else has told them, and therefore Moss will not know.
mike parker

Something that USED TO HAPPEN A LOT, was a "Mechanic" doing a brake cylinder REPAIR would find out that THE PARTS HE NEEDED WERE "NOT IN STOCK", so he would "SUBSTITUTE" brake parts FROM A DIFFERENT YEAR, MAKE OR MODEL, SOMETIMES NOT EVEN AN M.G.! If you had a "STANDARD-TRIUMPH MASTER CYLINDER", for example, your M.G. PARTS just might not fit correctly! Another problem was due to WILDCAT LABOR STRIKES IN THE U.K., where BMC/BLMC/British-Leyland (Their name changed a few times) would "WORK AROUND THE STRIKE" by having part of the car ASSEMBLED IN EUROPE! The "EURO-SPEC CAR" might not have the same parts as it's U.S./U.K. cousin!
I know FOR SURE that EACH EUROPEAN COUNTRY HAD THEIR OWN "STANDARD WIRING COLOR CODE" so that M.G. had to follow each country's "SPEC" to sell the car in that country!
wattswh1

This thread was discussed between 22/07/2005 and 27/07/2005

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